Composite resin molded body intended for acoustic member

Abstract

To provide a composite resin molded body with improved acoustic properties.SOLUTION: A composite resin molded body intended for an acoustic member includes a main resin and a fibrous filler dispersed in the main resin. A concentration of the fibrous filler is 50 wt.% or more in the composite resin molded body. Crystallinity of the main resin around the fibrous filler is higher than crystallinity of the main resin at other locations in the composite resin molded body.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a composite resin molded article for acoustic components that can realize a molded article with excellent sound characteristics. [Background technology]

[0002] So-called "general-purpose plastics," such as polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC), are not only very inexpensive, but also easy to mold and are a fraction of the weight of metals or ceramics. For this reason, general-purpose plastics are often used as materials for a variety of everyday items, such as bags, various types of packaging, various containers, and sheets, as well as industrial parts such as automobile parts and electrical parts, and as materials for daily necessities and miscellaneous goods.

[0003] However, general-purpose plastics have drawbacks, such as insufficient mechanical strength, and therefore do not have the sufficient properties required for materials used in various industrial products, including mechanical products such as automobiles, and electrical, electronic, and information products, and their range of application is currently limited.

[0004] On the other hand, so-called "engineering plastics" such as polycarbonate, fluororesin, acrylic resin, and polyamide have excellent mechanical properties and are used in various industrial products, including automobiles and other machinery products, as well as electrical, electronic, and information products. However, engineering plastics have issues such as being expensive, the difficulty of monomer recycling, and a large environmental impact.

[0005] Therefore, there is a demand for significant improvements in the material properties (mechanical strength, etc.) of general-purpose plastics. A known technique for strengthening general-purpose plastics is to disperse fibrous fillers such as natural fibers, glass fibers, and carbon fibers into the resin of the general-purpose plastic to improve its mechanical strength. It is known that adding these fibrous fillers not only improves mechanical properties but also acoustic characteristics by increasing the internal loss inherent to the material. Among these, organic fillers such as cellulose are attracting attention because they are inexpensive and environmentally friendly when disposed of.

[0006] In audio equipment such as speakers, headphones, and various players, molded parts used in their exterior and interior components require not only mechanical strength but also improved viscosity to improve internal loss in order to improve sound characteristics. Various companies are currently investigating ways to improve the sound characteristics of composite resins. For example, a composite resin made of cellulose fiber and thermoplastic resin has been proposed, containing approximately 35% cellulose fiber by weight, with a length of 0.5 to 1.0 mm and a fiber diameter of 50 to 60 μm (see, for example, Patent Document 1). Excellent sound characteristics have been achieved by using this composite resin as a molding composition for speaker unit mounting components. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 4179037 Summary of the Invention [Problem to be solved by the invention]

[0008] However, in the composite resin described in Patent Document 1, the moldability deteriorates when a large amount of fiber is added, so more than half of the composite resin is resin, which results in insufficient rigidity and internal loss, and insufficient sound characteristics.

[0009] The present invention is intended to solve the above problems, and has an object to realize a composite resin molding for acoustic components with improved sound characteristics. [Means for solving the problem]

[0010] In order to achieve the above object, the composite resin molding for acoustic components according to the present invention is a composite resin molding for acoustic components containing a base resin and a fibrous filler dispersed in the base resin, The concentration of the fibrous filler in the composite resin molding is 50% by weight or more, In the composite resin molding, the crystallinity of the base resin around the fibrous filler is higher than the crystallinity of the base resin in other locations. [Effects of the Invention]

[0011] The composite resin molding for acoustic components according to the present invention makes it possible to achieve both a high elastic modulus and a high internal loss in fiber-reinforced materials for acoustic components, thereby improving the sound characteristics of the product. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic view showing the internal structure of a composite resin molded body according to a first embodiment. [Figure 2A] 2 is a schematic diagram of a fibrous filler that is a constituent member of the composite resin molded product according to the first embodiment. FIG. [Figure 2B] FIG. 2B is a partial enlarged view including the end of the fibrous filler of FIG. 2A. [Figure 3] 1(a) is a 2D phase image display of a surface AFM image of the composite resin molded body according to the first embodiment, and FIG. 1(b) is a superimposed display of a 3D image and a phase image. [Figure 4] 1A to 1C are schematic diagrams illustrating a manufacturing process of a composite resin molded body according to the first embodiment. [Figure 5] Table 1 shows the measurement results for Examples 1 to 4 and Comparative Examples 1 to 4. DETAILED DESCRIPTION OF THE INVENTION

[0013] A composite resin molding for acoustic components according to a first aspect is a composite resin molding for acoustic components containing a base resin and a fibrous filler dispersed in the base resin, The concentration of the fibrous filler in the composite resin molding is 50% by weight or more, In the composite resin molding, the crystallinity of the base resin around the fibrous filler is higher than the crystallinity of the base resin in other locations.

[0014] A composite resin molding for acoustic components according to a second aspect may be the same as that according to the first aspect, wherein the crystallinity of the base resin around the tip of the fibrous filler in the composite resin molding is higher than the crystallinity of the base resin around the center of the fibrous filler.

[0015] The composite resin molding for acoustic components according to the third aspect may be the composite resin molding according to the first or second aspect, and may have holes or cracks on the surface of the composite resin molding, the width of which may be 1 / 10 or less of the diameter of the fibrous filler.

[0016] A composite resin molding for acoustic components according to a fourth aspect is any one of the first to third aspects, in which the fibrous filler in the composite resin molding does not have to be hydrophobized in advance.

[0017] A composite resin molding for acoustic components according to a fifth aspect is any one of the first to fourth aspects, wherein the fibrous filler in the composite resin molding may be defibrated only at the ends.

[0018] A composite resin molding for acoustic members according to a sixth aspect may be the composite resin molding for acoustic members according to any one of the first to fifth aspects, wherein the fibrous filler is a fiber made of natural fiber such as cellulose.

[0019] A composite resin molded product for acoustic members according to a seventh aspect is the composite resin molded product according to any one of the first to sixth aspects, wherein the main resin component is an olefin resin.

[0020] Hereinafter, a composite resin molding according to an embodiment will be described with reference to the drawings. In the following description, the same components are denoted by the same reference numerals, and the description thereof will be omitted where appropriate.

[0021] (Embodiment 1) Fig. 1 is a schematic see-through view showing the internal configuration of a composite resin molded product 10 according to embodiment 1. Fig. 2A is a schematic view of a fibrous filler 2 that is a constituent member of the composite resin molded product according to embodiment 1. Fig. 2B is a partial enlarged view including an end portion 5 of the fibrous filler of Fig. 2A. The composite resin molded body 10 according to the first embodiment is made of a melt-kneaded mixture containing a base resin 1, a fibrous filler 2, and an additive 3. As shown in the schematic see-through view of FIG. 1, the composite resin molded body has the fibrous filler 2 and the additive 3 dispersed in the base resin 1. The concentration of the fibrous filler 2 in the composite resin molded body 10 is 50% by weight or more. Furthermore, in the composite resin molded body 10, the crystallinity of the base resin 1 around the fibrous filler 2 is higher than the crystallinity of the base resin 1 in other locations. This makes it possible to achieve both a high elastic modulus and a high internal loss, thereby improving the sound characteristics of products that use this material.

[0022] <Main resin> In this embodiment, the base resin 1 is preferably a thermoplastic resin in order to ensure good moldability. Examples of thermoplastic resins include olefin resins (including cyclic olefin resins), styrene resins, (meth)acrylic resins, organic acid vinyl ester resins or derivatives thereof, vinyl ether resins, halogen-containing resins, polycarbonate resins, polyester resins, polyamide resins, thermoplastic polyurethane resins, polysulfone resins (such as polyethersulfone and polysulfone), polyphenylene ether resins (such as 2,6-xylenol polymers), cellulose derivatives (such as cellulose esters, cellulose carbamates, and cellulose ethers), silicone resins (such as polydimethylsiloxane and polymethylphenylsiloxane), rubber or elastomer (such as diene rubbers such as polybutadiene and polyisoprene, styrene-butadiene copolymers, acrylonitrile-butadiene copolymers, acrylic rubbers, urethane rubbers, and silicone rubbers), and biomass plastics (such as biopolyethylene, biopolyethylene terephthalate, starch, polylactic acid, polybutylene succinate, polyhydroxyalkanoic acid, and other bio-derived resins and biodegradable resins). The above resins may be used alone or in combination of two or more. Note that the base resin 1 does not have to be a thermoplastic resin as long as it has good moldability, and is not limited to the above materials.

[0023] Among these thermoplastic resins, the main resin 1 is preferably an olefin-based resin having a relatively low melting point. Examples of olefin-based resins include homopolymers of olefin-based monomers, copolymers of olefin-based monomers, and copolymers of olefin-based monomers with other copolymerizable monomers. Examples of olefin-based monomers include linear olefins (α-C2-20 olefins such as ethylene, propylene, 1-butene, isobutene, 1-pentene, 4-methyl-1-pentene, and 1-octene), and cyclic olefins. These olefin-based monomers may be used alone or in combination. Of the above olefin-based monomers, linear olefins such as ethylene and propylene are preferred. Other copolymerizable monomers include, for example, fatty acid vinyl esters such as vinyl acetate and vinyl propionate; (meth)acrylic monomers such as (meth)acrylic acid, alkyl (meth)acrylates, and glycidyl (meth)acrylate; unsaturated dicarboxylic acids or anhydrides such as maleic acid, fumaric acid, and maleic anhydride; vinyl esters of carboxylic acids (e.g., vinyl acetate and vinyl propionate); cyclic olefins such as norbornene and cyclopentadiene; and dienes such as butadiene and isoprene. These copolymerizable monomers may be used alone or in combination. Specific examples of olefin-based resins include copolymers of linear olefins (e.g., α-C2-4 olefins), such as polyethylene (e.g., low-density, medium-density, high-density, or linear low-density polyethylene), polypropylene, ethylene-propylene copolymers, and terpolymers such as ethylene-propylene-butene-1.

[0024] <Dispersant> Next, the dispersant will be described. The composite resin molded body of this embodiment may contain a dispersant for the purpose of improving the adhesion between the fibrous filler 2 and the base resin 1 or the dispersibility of the fibrous filler 2 in the base resin 1. Improved dispersibility results in uniform dispersion at the interface between the fiber and the resin, increasing vibration absorption at the interface and improving sound characteristics. Examples of dispersants include various titanate-based coupling agents, silane coupling agents, unsaturated carboxylic acids, maleic acid, maleic anhydride, or modified polyolefins grafted with their anhydrides, fatty acids, fatty acid metal salts, and fatty acid esters. The silane coupling agents are preferably unsaturated hydrocarbon-based or epoxy-based. The surface of the dispersant may be modified by treating it with a thermosetting or thermoplastic polymer component. The content of the dispersant in the composite resin molded body of this embodiment is preferably 0.01% by mass or more and 20% by mass or less, more preferably 0.1% by mass or more and 10% by mass or less, and even more preferably 0.5% by mass or more and 5% by mass or less. If the dispersant content is less than 0.01% by mass, poor dispersion occurs, while if the dispersant content exceeds 20% by mass, the strength of the composite resin molding decreases. The dispersant is appropriately selected depending on the combination of the main resin 1 and the fibrous filler 2, but if a dispersant is not required, it does not need to be added.

[0025] <Fiber filler> Next, we will explain the fibrous filler 2. The fibrous filler 2 (hereinafter, may be simply referred to as "fiber") contained in the composite resin molding in this embodiment is used primarily for the purpose of improving the mechanical properties and improving dimensional stability by reducing the linear expansion coefficient in the composite resin molding molded using the composite resin composition. For this purpose, the fibrous filler 2 preferably has a higher elastic modulus than the base resin 1. Specific examples include carbon fiber, carbon nanotubes, pulp, cellulose, cellulose nanofiber, lignocellulose, lignocellulose nanofiber, basic magnesium sulfate fiber (magnesium oxysulfate fiber), potassium titanate fiber, aluminum borate fiber, calcium silicate fiber, calcium carbonate fiber, silicon carbide fiber, wollastonite, xonotlite, various metal fibers, natural fibers such as cotton, silk, wool, and hemp, regenerated fibers such as jute fiber, rayon, and cupra, semi-synthetic fibers such as acetate and promix, synthetic fibers such as polyester, polyacrylonitrile, polyamide, aramid, and polyolefin, and modified fibers chemically modified on the surface and ends of these fibers. Furthermore, among these, carbons and celluloses are particularly preferred from the viewpoints of availability, high elastic modulus, and low linear expansion coefficient.

[0026] The second purpose of adding fibrous filler 2 is to improve sound characteristics, i.e., viscosity. For this purpose, it is preferable that the fibrous filler has a certain degree of flexibility, and natural fibers such as pulp, cellulose, cellulose nanofiber, lignocellulose, lignocellulose nanofiber, cotton, silk, wool, or hemp, or recycled fibers such as jute fiber, rayon, or cupra are preferred. Fibers with flexibility other than those listed above can also be used for this purpose. However, fibrous filler 2 is not limited to the above materials as long as they can improve mechanical properties and are flexible.

[0027] Next, we will explain the morphology near the interface between the fibrous filler 2 and the base resin 1. To improve sound characteristics, i.e., internal loss, it is necessary to convert vibrations into thermal energy. In composite resins, internal loss is improved by generating frictional heat due to vibration at the interface between the fibrous filler and the resin. To achieve this, as mentioned above, the flexibility of the fibrous filler facilitates conversion to vibration energy, improving internal loss. Furthermore, controlling the crystalline state of the resin surrounding the fibrous filler 2 can further improve internal loss. As shown in the enlarged partial view of the end 5 of the fibrous filler in Figure 2B, a structure that satisfies the above criteria can be achieved by defibrating only the end 5 of the fibrous filler. This structure allows for a higher degree of crystallinity near the tip of the fibrous filler compared to the center. The more shear force is increased during kneading, the more defibration occurs, and the more defibration occurs, the higher the degree of crystallinity. Differences in crystallinity create strength differences in the resin, resulting in the creation of an interface. The creation of an interface allows vibration absorption at the interface, improving internal loss. The tip defibrated portion preferably accounts for 5% or more and 50% or less of the entire fiber length L of the fibrous filler 2. If the defibrated portion is less than 5% of the entire fiber length L, the specific surface area is small, so no increase in crystallinity is observed. If it is 50% or more, the interfaces due to differences in crystallinity do not increase, and in either case, the sound characteristics deteriorate. Furthermore, near the center of the fiber, there are areas that are in close contact with the resin and areas that are not, and the crystallinity of the intimate areas is higher than that of the non-intimate areas. By increasing the number of interfaces, internal loss can be improved. This structure can be achieved by kneading the fibrous filler without prior hydrophobic treatment. Furthermore, by using fibers with defibrated tips, the center is not defibrated and the surface area does not increase significantly, so the resin does not thicken. This maintains fluidity even at high concentrations, improving moldability.

[0028] Next, the state of the fibrous filler in a composite resin molded body will be described. Depending on the molding conditions, it is possible to cause the fibrous filler to segregate near the surface of the molded body. When natural materials are used as the fibrous filler, tiny voids are present in the fibers. Therefore, by segregating the fibrous filler near the molded body, tiny voids can be present on the surface of the molded body. Furthermore, as mentioned above, if the fibrous filler is not pre-treated to be hydrophobic, the base resin and the fibrous filler do not blend well, and tiny gaps can be present between the base resin and the fibrous filler due to differences in thermal shrinkage during molding. These gaps can also be segregated to the surface of the molded body depending on the molding process. In this way, having tiny holes or cracks on the surface of the molded body can enhance sound absorption characteristics and improve sound characteristics due to the principle of Helmholtz resonance, as with perforated plate walls.

[0029] Fig. 3(a) is a 2D phase image display of an atomic force microscope (AFM) image of the surface of the composite resin molded product according to embodiment 1. Fig. 3(b) is a superimposed display of a 3D image and a phase image. As shown in Figure 3(a), the composite resin molding has tiny holes and cracks 6 near its surface. Sound characteristics can be further improved by controlling the width of the tiny holes and cracks 6 near the surface of the composite resin molding. It is desirable that the width of the short side of the holes and cracks 6 be 1 / 10 or less of the diameter of the fibrous filler. The upper limit of the width of the short side of the holes and cracks 6 has been determined through simulation; if it is greater than 1 / 10 of the filler diameter, resonance will not occur inside the holes, and sound characteristics will not be sufficiently improved. Therefore, it is desirable that it be 1 / 10 or less of the diameter of the fibrous filler. Such cracks 6 can be controlled by the original fiber state, the difference in thermal shrinkage between the resin and fiber, and the molding conditions.

[0030] When pellets of a composite resin composition used to manufacture a composite resin molded body are applied to primary exterior components such as the exterior body of a speaker, the composite resin composition containing a fibrous filler is required to have colorability. For the composite resin composition to have colorability, the whiteness of the composite resin composition must be maintained, and the whiteness of the added fibrous filler must also be maintained. A high L value, as determined by color difference measurement, is preferable for the fibrous filler. The L value (brightness) in the Lab color system of a fibrous filler that improves the colorability of the molded body has been experimentally calculated, and an L value of 85 or higher is preferred.

[0031] Next, the characteristics of the fibrous filler 2 will be described. The types of the main resin 1 and the fibrous filler 2 are as described above. However, if the fibrous filler 2 is too soft relative to the main resin 1, i.e., if the elastic modulus is small, the composite resin composition and the composite resin molded product after molding will have a low overall elastic modulus, resulting in reduced strength. On the other hand, if the fibrous filler 2 is too hard relative to the main resin 1, i.e., if the elastic modulus is large, sound vibrations will not be sufficiently damped during damping, resulting in poor sound characteristics. Therefore, in the relationship between the elastic moduli of the main resin 1 and the fibrous filler 2, it is preferable that the elastic modulus of the fibrous filler 2 be higher, and that the difference between them be as small as possible. The optimal relationship is calculated from simulation results, and it is preferable that the difference in elastic modulus between the main resin 1 and the fibrous filler 2 be within 20 GPa.

[0032] Furthermore, the fibrous filler is present in the composite resin molding in an amount of 50% by weight or more, which makes it possible to achieve excellent sound characteristics and a high elastic modulus.

[0033] <Method of manufacturing composite resin molded body> Next, a method for manufacturing the composite resin molded body will be described. Fig. 4 is a flow diagram illustrating an example of a manufacturing process for the composite resin molded body according to the first embodiment. (1) The base resin, fibrous filler, and additives are placed in a melt-kneading processing device and melt-kneaded within the device. This melts the base resin, and the fibrous filler and additives are dispersed into the molten base resin. At the same time, the shearing action of the device promotes the defibration of agglomerates of fibrous filler, allowing the fibrous filler to be finely dispersed within the base resin. The ends of the fibrous filler are also defibrated at this time.

[0034] Conventionally, fibrous fillers have been used after the fibers have been defibrated in advance through pretreatment such as wet dispersion. However, when defibrating fibrous fillers in advance in the solvent used in wet dispersion, they are more easily defibrated than when defibrated in a molten base resin, making it difficult to defibrate only the ends, and the entire fibrous filler ends up in a defibrated state. In addition, adding pretreatment increases the number of processes, resulting in issues such as reduced productivity.

[0035] In contrast, in the manufacturing process for the composite resin molding in this embodiment, a pretreatment by wet dispersion for the purpose of defibrating the fibrous filler is not performed, and instead a melt-kneading treatment (all-dry method) is performed together with the base resin, dispersant, etc. In this method, by not performing a wet dispersion treatment of the fibrous filler, it is possible to partially defibrate only the ends of the fibrous filler as described above, and the number of steps is reduced, thereby improving productivity.

[0036] To produce the fibrous filler of the present embodiment by an all-dry method, it is preferable to apply high shear stress during kneading, and specific kneading methods include a single-screw kneader, a twin-screw kneader, a roll kneader, a Banbury mixer, and combinations thereof. From the viewpoint of being able to easily apply high shear and being highly suitable for mass production, a continuous twin-screw kneader and a continuous roll kneader are particularly preferable. Kneading methods other than those mentioned above may also be used as long as they are capable of applying high shear stress.

[0037] (2) The composite resin composition extruded from the melt kneading device is cut into pellets using a pelletizer, etc. Pelletization methods include in-air hot cutting, underwater hot cutting, and strand cutting, which are carried out immediately after the resin is melted, as well as crushing and cutting methods, such as molding a molded body or sheet.

[0038] (3) By injection molding the pellets, an injection-molded article can be produced as a composite resin molding. By mixing the fibrous filler in the pellets as described above, an injection-molded article with excellent elastic modulus, impact resistance, and appearance can be obtained.

[0039] Hereinafter, examples and comparative examples of the experiments conducted by the inventors will be described.

[0040] Example 1 In Example 1, a pulp-dispersed polypropylene composite resin molding was produced by the following production method.

[0041] (1) Softwood pulp (product name: NBKP Celgar, manufactured by Mitsubishi Paper Mills, Ltd.) was used as the starting material for the fibrous filler. This softwood pulp was crushed in a crusher to obtain the fibrous filler. The end defibration was adjusted during the crushing process. (2) A mixture of polypropylene (manufactured by Prime Polymer Co., Ltd., product name: J108M) as the base resin, the above-mentioned fibrous filler, and maleic anhydride (manufactured by Sanyo Chemical Industries, Ltd., product name: Umex) as the additive were weighed out and dry-blended so that the weight ratio of base resin to fibrous filler to additive was 42.9:55.0:2.1. (3) The mixture was then melted, kneaded, and dispersed in a twin-screw kneader (KRC Kneader, manufactured by Kurimoto Iron Works Co., Ltd.). The shear force can be adjusted by changing the screw configuration of the twin-screw kneader, and a medium shear type was used in Example 1. The molten resin was hot-cut to produce pulp-dispersed polypropylene pellets.

[0042] (4) Using the prepared pulp-dispersed polypropylene pellets, composite resin molded specimens were prepared using an injection molding machine (180AD manufactured by Japan Steel Works). The specimen preparation conditions were a resin temperature of 190°C, a mold temperature of 60°C, an injection speed of 60 mm / s, and a holding pressure of 80 Pa. The specimen shape was varied depending on the evaluation items described below. Size 1 dumbbells were prepared for elastic modulus measurement, and 60 mm square, 1.6 mm thick flat plates were prepared for hydrophilicity measurement. The obtained pulp-dispersed polypropylene composite resin molded specimens were evaluated using the following methods.

[0043] (Fiber end defibration) The resulting pulp-dispersed polypropylene pellets were immersed in xylene to dissolve the polypropylene, and the shape of the remaining pulp fibers was observed using an SEM. The ends of the fibers were found to be defibrated.

[0044] (Elastic modulus of composite resin molded body) A tensile test was carried out using the obtained No. 1 dumbbell-shaped test piece. Here, the elastic modulus was evaluated as follows: if the value was less than 3.0 GPa, it was marked x; if it was 3.0 GPa or more but less than 4.0 GPa, it was marked △; if it was 4.0 GPa or more, it was marked ◯. The elastic modulus of this test piece was 4.3 GPa, and it was marked ◯.

[0045] (Evaluation of sound characteristics of composite resin moldings) The resulting test specimens were used to evaluate their sound characteristics through viscoelasticity testing. Specifically, tan δ, which is linked to sound absorption characteristics, was calculated from the viscoelasticity measurement results, and sound vibration absorption was evaluated. A simple speaker enclosure was also created, and sound was generated inside it, followed by a human sensory evaluation. The sensory evaluation confirmed that a higher tan δ indicated a better sound with less intermixing, while a lower tan δ indicated a poorer sound with more residual sound and noise. For sound vibration absorption, a test specimen with a tan δ 0.05 or more lower than that of a current resin speaker was rated as ×; a test specimen with a tan δ within ±0.05 of that of the current resin speaker was rated as △; a test specimen with a tan δ 0.05 or more higher than that of the current resin speaker was rated as 〇; and a test specimen with a tan δ 0.1 or more higher than that of the current resin speaker was rated as ◎. The test specimen's sound characteristics were evaluated as ◎.

[0046] Example 2 In Example 2, the fibrous filler concentration was changed to 70% by weight, the base resin was changed to 27.9% by weight, and the other material conditions and process conditions were the same as in Example 1 to produce pulp-dispersed polypropylene pellets and molded bodies. Evaluations similar to those in Example 1 were also carried out.

[0047] Example 3 In Example 3, pulp-dispersed polypropylene pellets and a molded body were produced in the same manner as in Example 1, except that the rotation speed during kneading was reduced to a low shear force that would not defibrate the ends of the fibrous filler. Evaluations were also carried out in the same manner as in Example 1.

[0048] Example 4 In Example 4, pulp-dispersed polypropylene pellets and a molded body were produced in the same manner as in Example 1, except that the pre-crushing conditions for the pulp, which is a fibrous filler, were changed so that the cracks caused by the pulp in the molded body would become larger. Evaluations similar to those in Example 1 were also carried out.

[0049] (Comparative Example 1) In Comparative Example 1, the fibrous filler concentration was changed to 30% by weight, the base resin was changed to 67.9% by weight, and the other material conditions and process conditions were the same as in Example 1 to produce pulp-dispersed polypropylene pellets and a molded body. Evaluations similar to those in Example 1 were also carried out.

[0050] (Comparative Example 2) In Comparative Example 2, the starting pulp was hydrophobized in advance with a silane coupling agent, and the other material and process conditions were the same as in Example 1 to produce pulp-dispersed polypropylene pellets and a molded body. Evaluations similar to those in Example 1 were also carried out.

[0051] (Comparative Example 3) In Comparative Example 3, the molding conditions were changed to allow extremely slow cooling so that the crystallinity of the resin near the fibrous filler was approximately the same as that of the other areas, and the crystallinity of the resin around the tip and center of the fibrous filler was also approximately the same. Otherwise, pulp-dispersed polypropylene pellets and a molded body were produced in the same manner as in Example 1. Evaluations were also performed in the same manner as in Example 1.

[0052] Comparative Example 4 In Comparative Example 4, except that short glass fibers were used as the fibrous filler, pulp-dispersed polypropylene pellets and a molded body were produced in the same manner as in Example 1. The same evaluations as in Example 1 were also carried out.

[0053] The measurement results for each of Examples 1 to 4 and Comparative Examples 1 to 4 are shown in Table 1 of FIG.

[0054] As is clear from Table 1 in Figure 5, in Example 2, in which the fibrous filler concentration was changed to 70 wt%, the modulus of elasticity increased as the concentration increased, but the way the resin crystallized and the cracks on the surface of the molded body were the same as in Example 1, and it was confirmed that the sound characteristics were also good. It was confirmed that if the fibrous filler was end-defibrated and not pre-treated to be hydrophobic, the crystallinity near the fibrous filler was greater than the crystallinity in areas other than the vicinity of the fibrous filler, and even with regard to the crystallinity near the fibrous filler, the crystallinity near the tip was greater than the crystallinity near the center of the fibrous filler, and the crack width near the surface of the molded body was 1 / 10 or less of the filler diameter, a composite resin with a high modulus of elasticity and good sound characteristics could be obtained.

[0055] In Example 3, where the fibrous filler was not defibrated at the ends, the degree of crystallinity near the tip of the fibrous filler was almost equal to the degree of crystallinity near the center of the fibrous filler, and the number of interfaces with differences in elastic modulus was reduced, resulting in sound characteristics that were not as good as those in Example 1.

[0056] In Example 4, in which the cracks caused by the pulp were made larger when the molded body was formed, the sound absorption properties were deteriorated, and the sound characteristics were not as good as in Example 1.

[0057] In Comparative Example 1, in which the fibrous filler concentration was set to 30% by weight, the elastic modulus was low and the sound characteristics were also poor.

[0058] In Comparative Example 2, where the starting pulp was pre-treated for hydrophobicity, the crystallinity near the fibrous filler was nearly equal to that of the rest of the fibrous filler. The crystallinity near the tip of the fibrous filler was also nearly equal to that near the center of the fibrous filler. Furthermore, the resin and the fibrous filler were well integrated, and there were no cracks on the surface of the molded product. These factors resulted in poor sound characteristics.

[0059] In comparison example 3, in which the degree of crystallinity of the resin near the fibrous filler was approximately the same as the degree of crystallinity elsewhere, and in which the degree of crystallinity of the resin around the tip and center of the fibrous filler was also approximately the same, the sound characteristics were slightly worse.

[0060] In Comparative Example 4, in which glass short fibers were used as the fibrous filler, the modulus of elasticity was considerably high, but the sound absorption was poor, and the sound characteristics were not as good as in Example 1.

[0061] From the above evaluation, it was confirmed that a composite resin molding with a high elastic modulus and good sound characteristics can be obtained if the fibrous filler content is 50% by weight or more, the ends of the fibrous filler are defibrated and not pre-treated to be hydrophobic, the crystallinity near the fibrous filler is greater than the crystallinity of areas other than the fibrous filler, and even with regard to the crystallinity near the fibrous filler, the crystallinity near the tip is greater than the crystallinity near the center of the fibrous filler, and the crack width near the surface of the molding is 1 / 10 or less of the filler diameter.

[0062] In addition, the present disclosure includes appropriate combinations of any of the various embodiments and / or examples described above, and can achieve the effects of each embodiment and / or example. [Industrial Applicability]

[0063] The composite resin molded product for acoustic components according to the present invention can provide a molded product with superior mechanical strength and sound characteristics compared to conventional general-purpose resins. The composite resin molded product for acoustic components according to the present invention can improve the sound characteristics of the base resin, and can therefore be used as acoustic components such as speakers, housing components for sound-emitting electronic devices and home appliances, a substitute for engineering plastics, or a substitute for metal materials. It can also be used as a building material or an automobile component. [Explanation of symbols]

[0064] 1. Base resin 2. Fibrous filler 3 Additives 4 Defibration site 5 End 6. Crack

Claims

1. A composite resin molding for acoustic components, comprising a base resin and a fibrous filler dispersed in the base resin, The concentration of the fibrous filler in the composite resin molding is 50% by weight or more, A composite resin molding for acoustic components, wherein the crystallinity of the base resin around the fibrous filler is higher than the crystallinity of the base resin in other areas of the composite resin molding.

2. A composite resin molding for acoustic components as described in claim 1, wherein in the composite resin molding, the crystallinity of the base resin around the tip of the fibrous filler is higher than the crystallinity of the base resin around the center of the fibrous filler.

3. 3. The composite resin molding for acoustic components according to claim 1, wherein the surface of the composite resin molding has holes or cracks, the width of which is 1 / 10 or less of the diameter of the fibrous filler.

4. 4. The composite resin molding for acoustic members according to claim 1, wherein the fibrous filler in the composite resin molding is not preliminarily hydrophobized.

5. The composite resin molding for acoustic members according to claim 1 , wherein only the ends of the fibrous filler in the composite resin molding are defibrated.

6. 6. The composite resin molding for acoustic components according to claim 1, wherein the fibrous filler is a fiber made of natural fiber such as cellulose.

7. The composite resin molding for acoustic components according to claim 1 , wherein the main resin is an olefin resin.

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